The portal system
toggles lights visibility to "true" only when you can see
them, tremendously improving the performance. The performance gain
will depend on your level layout and number of dynamic lights.

All you need to
do is setup portals and zones (like explained in the tutorial)

All the lights,
and this include point lights, spot lights and all the lights
attached in blueprints inside a zone will be set to "visible"
when:

You are
inside the zone

The zone
is visible through a portal

The portal
visibility check is based on Unreal Engine built in HZB occlusion, so
it's extremely fast and efficient performance wise.

To give you a
performance idea, we have tested in levels from 4000 to 25 000
actors, with 50 to 500+ dynamic lights, more than half of them
casting shadows. Volumetric lighting enabled.

We're getting 30
to 60% performance improvement with this system, making them playable
on low end gaming computers (8 years old i7 950 processor and GTX 950
graphic card).